Control system



June 19, 1951 A. J. HORNFECK 2,557,224

CONTROL SYSTEM Filed June 29, 1945 3 Sheets-Sheet 1 MOTOR CONTROL (7 POWER CONTROLLER AMPLIFIER l6 L ELECTRIC FURNACE INVENTOR.

ANTHONY J. HOR-NFECK FIG.

June 19, 1951 A. J. HORNFECK 2,557,224

CONTROL SYSTEM Filed June 29, 1945 V s Sheets-Sheet a CONTROLLER 25 34 f: l\

AND

MOTOR CONTROL J INVENTOR.

ANTHONY J. HORNFECK Patented June 19, 1951 CONTROL SYSTEM Anthony J. Hornfeck, Cleveland Heights, Ohio,

"asslgnor to Bailey Meter tion of Delaware Company, a corpora- Appllcatlon June 29, 1945, Serial No. 602,334

The present invention relates to measuring and/or control systems, particularly of the electronic circuit type. tity, position or other value which may be represented by and electrical resistance value may be continuously and instantaneously measured through the agency of the circuit to be described. The measurement so obtained may be used to effect a control of the same or of another variable which may or may not contribute to the magnitude or change in magnitude of the variable being measured.

Specifically, my present invention provides improvements in an electronic control circuit allowing the control standard to be set at more than one physical location without interfering with the measurement or control and allowing observation of the actual value of the variable as well as its relation to thedesircd standard value at more than one physical location.

I have chosen to illustrate and describe my invention in connection with three basic electronic measuring circuits representative only and not limited thereto. In general, I describe my invention in connection with a phase sensitive alternating current bridge network including a resistance thermometer. A second embodimentis in connection with a movable core transformer telemetering circuit. The third embodiment is in connection with a thermocouple type of temperature measuring instrument. I have chosen these as-repre'sentative only and by way of example.

n the drawings:

Fig. l is a measuring and control system in connection with a resistance thermometer.

Fig. 2 is a graph of circuit values for a voltage discrimination indicator.

Fig. 3 is a portion of a circuit applicable to the general arrangement'of Figs. 1, 4 and 5.

Fig. 4 is a measuring and control system applied to a telemetric flow meter.

Fig. 5 is a measuring and control circuit applied to a thermocouple temperature measurement.

All of the figures of the drawing are shown in quite diagrammatic or schematic manner. In Fig. 1 I have shown the amplifier and motor control circuit in detail. I have not felt it necessary to duplicate such detail in Figs. 4 and 5 and have therein indicated the amplifier and motor control circuits merely as blocks. The showing of Fig. 3 is of push button and signal light means applicable to the general embodiments to allow the operator at either the instrument or at the remote. location to assume control of the system and to indicate where such control is placed.

11 Claims. (Cl. 323-15) A variable condition, quan- Referring now in particular to Fig. 1, I indicate at I a. phase sensitive alternating current bridge having fixed resistor arms 2, 3 and l. The fourth arm 5 of the bridge I is a resistance element located in an electric furnace 6 and sensitive to.

the temperature thereof. For balancing the network I provide an adjustable resistance I inserted between the arms 3 and 4 and provided with a movable contact arm 8 for proportioning the resistance 1 between the arms 3 and 4.

For positioning the contact arm 8 I provide a motor 8 which also positions an indicator l0 relative to a scale H and relative to a revoluble chart I 2, thereby providing an instantaneous indication as well as acontinuous record of the value of temperature to which the resistance arm 5 is sensitive.

The electric furnace 6 is preferably heated by electric resistance elements [3 receiving current from an alternating current source It which also provides alternating current supply to the bridge i through a transformer l5.

Preferably the bridge arm 5 is a platinum resistance measuring element. The conjugate corners of the bridge I are connected to an amplifier l6 and motor control ll for the motor 9. For an understanding of a phase sensitive alternating current bridge for measuring the resistance of the.

leg 5 subjected to temperature of the furnace 6 reference may be had to the Ryder Patents 2,275,317 and 2,333,393. The conjugate voltage supplied to the amplifier I6 assumes a balance or unbalance and a phase relation relative to the supply voltage dependent upon the magnitude and sense of the unbalanced conditions of the bridge. The amplifier is selectively controls motor tubes l8, IS. The tubes l8, l9 control the amount and direction of unbalance of saturable core reactors 20, 2| for directional and speed control of a capacitor-run motor 9 adapted to position the arms 8, lil.

The motor 9 is of an alternating current type having windings 22 and 23 ninety electrical degrees apart and also having a capacitor 24. When alternating current flows directly through one of the windings and simultaneously through the other winding in series with the capacitor the motor rotates in predetermined direction and at a speed determined by the extent of unbalance oi the saturable core reactors 20, 2|. It is not necessary to go into greater detail as to the construction and operation 01' the amplifier l6 and the motor control circuit H, as reference may be had to the above mentioned Ryder patents.

In my present invention, in addition to providactress an instantaneous indication and a continuous record of the value of temperature to which the arm 5 is subjected, I provide an electrical control of the heat input of the resistor l3 to an electric furnace 6. I have shown in this connection a power controller 25 which forms no part of the present invention. This may be a General Electric Reactrol or any other adaptable power controller for the resistor I3. My invention applies to the power controller 25 the establishment of an electric value eo bearing a, desired relation to the temperature to which the arm 5 is subjected, or to the deviation in such temperature from a standard or desired value.

The motor 9, positioning the contact arm 8, simultaneously positions a contact arm 23 over a slide wire 21. At 28 I indicate a contact arm adapted to be manuall positioned along a slide wire 29 for establishing the temperature standard to which the control works, i, e. the temperature value which is desirably maintained at the arm 5.

The parts 26, 21, 28 and 23 are included in a phase discriminatory circuit, including the joining conductors 30, 3|. This circuit is supplied with alternating current power through a transformer 32' connected across the source It. The contact arm 26 is positioned relative the slide wire 21 by the motor 9 representative of actual temperature to which the resistance arm 6 is sensitive. The contact arm 28 is positioned relative the slide wire 23 manually to a point representing the desired temperature. The phase discriminatory circuit including these elements then establishes a signal en across the terminals 32, 33 and 34, 35 of reversible phase and having a. magnitude proportional to the unbalance of the control circuit.

The operation is asfollows. within the furnace 6 deviates from the desired value, then the resistance of the bridge arm 5 changes, causing an unbalance of the bridge I in one directionor the other dependent upon whether the actual temperature is above or below the desired temperature. The phase and magnitude of the A.-C. output of the bridge I follows the sense and amount of unbalance of the bridge and is applied to the amplifier I6 for control of the motor 9. The motor 9 rotates in predetermined direction and amount determined by the phase and amount of unbalance of the bridge I and positions the contact 8 along the slide wire I in proper direction to rebalance the bridge. The amount of movement of the contacts over the slide wire I to bring about such a rebalancing is representative of the deviation of the actual temperature from the desired temperature, and therefore the indicator I3 continuously shows on the index it and chart I2 the actual temperature of the furnace.

At the same time the motor 9 has positioned the contact 26 along the slide wire 27 in consonance with the departure of the temperature from the desired temperature. With such movement of the contact arm 26 the phase discriminatory circuit including the elements 26, 21, 28, 29, 30 and 3| becomes unbalanced and an electrical value is established across the terminals 32, 33 representative of the direction and extent of such unbalance. Such signal is simultaneously efiective at the terminals 34, 35 controlling the power input to the resistor I3 in proper amount and direction to return the temperature of the furnace to the desired standard.

As the temperature (due to a change in heating of the resistor l3) returns toward desired value If temperature I tact 31.

4 the consequent temperature change at the resistor B unbalances the bridge I and causes the motor 9 to position the contacts 8 and 26 in proper direction and amount until the bridge I and the control bridge are again balanced. It is appreciated, of course, that this action may be more or less continuous, i. e. before the temperature returns completely to its desired standard there may be other influences acting upon the furnace to prevent or to accelerate the return of the temperature to the desired value. In other words, the measuring circuit is continually indicating the instantaneous temperature of the furnace and the control circuit is continuously regulating the power controller 25 to maintain the temperature at the desired value or standard.

It is customary for an instrument, such as a recorder-controller, to contain the elements of the bridge I (except the resistance 5), the amplifier, the motor control, the motor 9, the recording measuring elements, and the control bridge. The slide 26 is positioned by the motor 9 relative to the slide wire 21 simultaneously with a positioning of the elements 8 and III. In other words all elements of Fig, 1 above the power lines I4. The hand adjusted slide 28 is usually provided with a knob and given ready access to the operator at the measuring controlling instrument. Such instrument may be located adjacent the furnace 6.

It; is frequently desired to have means provided at another or remote location wherein the control standard may be there adjusted and with provision for indicating at such remote location whether or not the temperature is being controlled to the desired standard value. At 36 I show by dotted enclosure such a remote station including a second standard setter comprising a manually positionable contact arm 31 along a slide wire 38 and having a scale 39 to show what temperature standard the elements 31, 38 are adjusted to. The slide wire 38 is connected across the conductors 30, 3! in parallel with the slide wire 29.

As shown in Fig. l a two-position switch so allows the control terminal 34 to be selectively connected with either the contact 28 or the con- As shown, it is connected to the contact 28 and therefore the phase discriminatory circuit includes the elements 28, 29 and does not include the element 31. If, at the remote location 36 the operator desires to change the temperature standard to which the power controller 25 operates he would move the arm of the switch 43 to the alternate position connecting the terminal 34 with the contact 37 and while doing this would hold depressed the push button 35 to open the circuit to the power controller momentarily while the switch-over is made.

If the power controller 25 draws current from the control bridge, the output or unbalance voltage will be reduced. Under this condition the deflection of the deviation indicator will not be an accurate function of temperature deviation from the control setting. If a more accurate reading is desired the controller can be momentarily disconnected by depressing the push button 4|. Thereafter the operator might turn the knob of contact 31 until the index 33 showed the new temperature standard he desires to maintain in the furnace and so long as the switch 40 connects the arms 31 with the terminal 34 the furnace would be controlled to the standard set on the indicator 33 with the elemen s 36. 21, 80.

9|, 31 and 99 comprising the phase discriminatory circuit.

Under the conditions just described where control of the standard is at the remote location, there is available at the measuring instrument a continuous indication of the actual temperature (II, II, l2), but no indication as to what standard is being used for the control because the elements 28, 29 are not in circuit. At the remote location the position of the switch 49 shows that the remote standard is being used and the position of the arm 91 relative to the scale 99 shows the value of the standard. I will now describe meanswithin the remote location 35 for showing at that location a deviation of temperature from the standard value and thereby, in conjunction with the scale 39, an indication of the actual temperature of the furnace. Such means is a cathode follower circuit 41 unique in that I use alternating current on the plates. Such circuit includes a zero center scale direct current voltmeter 42 under the control of tubes 49, 44. The variable resistance 45 provides a zero adjustment for the voltmeter 42, while the switch arm 46 allows a selective change in range of the voltmeter.

The cathode follower circuit 41 is connected in parallel across the terminals 94, 95 and is thus sensitive to the phase and magnitude of the signal applied to the power controller 25. If the signal 60 is of plus phase alternating current voltage the needle of the voltmeter 42 will swing to one side of its center zero. If the signal is of minus phase the needle will swing to a position the other side of its center zero. The

amount of such swing away from'zero is determined by the magnitude of the signal ea and in conjunction with the range of the voltmeter 42 then in use as determined by the position of the arm 45 selectively between several possible ranges.

In Fig. 2 I show an actual calibration curve of such a uro center scale direct current voltmeter and it will be observed that the motion is substantially linear throughout a major portion of the deviation each way from center zero. It will also'be noted that the circuit 41 provides an amplification of app oximately two in that the D.-C. volt output applied to the instrument 42 is approximately twice the value of ea in aiternating current voltage. a

It will be observed that the circuit 41 and in strument 42 are eifectively in circuit irrespective as to whether the elements 29, 29 or the elements 91, 99 are in use (connected in circuit) as a desired standard setting.

Referring now to Fig. 3, I show therein devices and circuits which may be superimposed upon the arrangement of Fig. 1 if desired. Inasmuch as this circuit and device are applicable to the arrangements of Figs. 1, 4 and 5 I have shown it as a separate figure which may be superimposed upon any one of the other three mentioned. At the instrument location I show instantaneous push buttons IA and RA as well as indicating lights I and R. -At the remote station 36 I show instantaneous push buttons 13 and RB as well as signal light I and R. Interconnecting the push buttons and signal lights is a relay 49 having a solenoid winding 49. In Fig. 3 the relay 49 is shown in deenergized position corresponding to a use of the standard setter 28,29 in the instrument location. By following the circuit through it will be seen that lights I (representing instrument location) are energized. that contact 28 is connected to terminal 99 and contact 31 is not so connected. Thus at both the instrument location and at the remote station the signal lights (1) indicate that control is at the instrument location under standard setter 28, 29 and the discrimination voltmeter 42 shows, at the remote station 39, the departure, if any, of temperature in one direction or the other from the standard.

Ii! it is desird to make the standard setting for control available at the remote-station by disconnecting contact 29 and connecting in the contact 31 and slide wire 39, then the instantaneous push button RA or the push button BB is momentarily depressed, thus energizing the coil 49 which is thereafter locked in through the push buttons IA and 1B. The signal lights (I) go out and the signal lights R are lighted, denoting that controlis at the remote station. Thereafter control may be returned to the instrument by momentarily depressing either IA or 1B which breaks the lock on coil 49 allowing it to become deenergized to the condition as shown in Fig. 3.

Thus I provideat either the instrument location or at the remote station signal lights which will show whether the control is under the standard control of elements 29, 29 or of elements 91, 39 while the deviation indicator 42 indicates at the remote location whether or not the desired standard (manually adjusted by 91, 99) is being attained.

In Fig. 4 I show an adaptation of my invention to a telemetering circuit including a movable core transformer. Such a circuit is disclosed and claimed in my copending application Serial No. 569,479, now Patent No. 2,439,891, to which reference may be had. I illustrate the measuring of the rate of flow of a fluid through a conduit 59 by a flow meter 5| sensitive to pressure difierentials existing across an orifice 52 inserted in the pipe line 59. The flow meter 5| is of a conventional U-tube type, the mercury level in one leg adapted to vertically position a core 53 relative to fixed windings 54, 55 and 54.,

Winding 54 is continuously energized across an alternating current source. Windings 55 and 56 are secondary windings receiving alternating cur rent inductively from the primary 54 and the whole comprising a movable core transformer.

The secondary windings 55, 55 are in loop circult with fixed resistances A and B of a receiver 51 having a slide wire 59 over which is positioned a movable contact 59 by a motor 69. Unbalance of the circuit, due to a movement of the core 53, is efiective upon the amplifier l6 and motor control I! for operating the motor 69 in proper direction and amount to move the contact 59 along the slide wire 58 and rebalance the circuit; The receiver 51 for indicating and/or recording, i. e. measuring the rate of fluid flow or difierential pressure, may be located adjacent the meter 5| or remote therefrom.

In Fig. 4 I adapt such a telemetering circuit to the control of the same or another variable from the continuous measurement of fluid flow through the orifice 52. In other words, the control impulse or signal of reversing phase and voltage magnitude may be used in a control of the rate of fluid flow through the conduit 59 or may be used in the control of some other variable in the same or another process.

The network conductors GI, 62 and 53 are connected to terminals 64, 55 and 66 respectively oi a control circuit including resistors C and D and slide wire 51. Thus the circuit elements C, D and 61 parallel the elements A, B and 58 across the windings 55, 56. The contact 68 is manually positioned along the slide wire 81 relative the scale 69 to establish the standard or value to which the control is to work. The signal value eo between the terminal 65 and the contact 68 is then efiective at the terminals 34, 35 of a power controller for controlling any variable as desired. At the same time the signal value eo is eilective at terminals 10, H entering the cathode follower circuit 41 for the cs M561 zero scale D.-C. voltmeter 42, otherwise designated as VI. Here, as previously described, the voltmeter 42 shows direction and amount of deviation of the actual rate of fluid flow as compared to the control standard established by the contact 68 along the slide wire 61. If desiredadditional voltmeters V2, V3, V4 may be connected across the terminals of the voltmeter VI and located at diiferent locations. With a low energy circuit it may require further amplification ahead of the phase discriminatory circuit as indicated by the box l2. Terminals l3, l4 indicate the possibility of utilizing the signal so for other power controllers or other phase discriminatory circuits. Likewise the terminals I5, 16 may be used following amplification l2.

In Fig. 5 I illustrate an adaptation of my invention to a thermocouple potentiometer circuit, such as is in general disclosed in my copending Ill application Serial No. 544,586, now Patent No.

2,447,338. Located within the furnace 6 is a thermocouple ll forming a part of a potentiometer circuit having a balancing slide wire 18 and contact 19, the latter positionable by the motor 9. The low level direct current signal in sense and magnitude determined by unbalance of the measuring circuit is applied to an alternating current bridge 80 having saturable core reactors 8|, 82 converting the low level D.-C. into reversible phase alternating current signals capable of unbalancing the bridge 80 in one direction or the other when temperature to which the thermocouple TI is sensitive departs from standard value.

The phase bridge 80 has its output connected to. the amplifier l6 and motor control H for control of the motor 9 in predetermined direction and speed for positioning the contact is alon the slide wire 18 to rebalance the measuring circuit. Simultaneously the motor 9 positions the contact 26 relative to the slide wire 21 of the circuit as previously described for establishing a control signal eo eilective at the terminals 36, 35 of the power controller 25 controlling the heating of the resistor elements E3 of the furnace 6.

It will thus be apparent that my invention is applicable to various types of measuring and controlling networks, of which I have described resistance thermometer, telemetering, and thermocouple circuits as by way of example. Other adaptations and advantages of the invention will be evident to those skilled in the art. Matter disclosed but not claimed herein is incorporated in divisional applications Serial Nos. 193,495 and 193,496, filed Novemmr 1, 1950.

What I claim as new, and desire to secure by Letters Patent of. the United States, is:

1. Apparatus for providing a control voltage of variable potential and phase comprising parallel .connected and A. C. excited slide wires, a contact on each slide wire, said contacts comprising the control voltage output, automatic means responslveto a variab.'e to actuate one contact in accordance with the value of said variable and manual means to actuate the other to set the normal for the output in respect to the desired value 01' the variable, an alternate control for said normal comprising a third slide wire always paralleling the first said wires, an adjustable contact on said third slide wire, switch means to selectively connect said last mentioned contact in place of the one used to set the output normal, a control voltage output circuit connected to said automatically actuated contact and to said switch means, and means actuated by said control voltage at the alternate control position to indicate the deviation between the normal setting and the automatic setting.

' 2. Apparaus for providing an adjustable control voltage of variable potential and phase comprising, in combination, a first slidewire having an adjustable contact, second and third slidewires connected in parallel with each other and with said first slidewire, said second and third slidewires each having an adjustable contact. means for connecting the ends of said slidewires to a source of A.-C., a switch having contacts connected to the adjustable contacts of said second and thirdslidew ires, a switch arm movable selectively into engagement with the switch contacts, a control voltage output circuit connected to the contact of said first slidewire and to said switch arm, and means connected across said output circuit to indicate the phase and potential of the control voltage, said last mentioned means comprising a cathode follower circuit having a pair or A.-C. energized triodes and a zero-center D.-C. voltmeter connected between the cathodes thereof.

3. Means for providing a control voltage of variable phase and potential comprising in combination, a transformer having an A. C. energized primary, a center tapped Secondary and a core movable under the influence of a variable to favor inductionto one or the other section of said secondary, a resistor shunting said secondary and having a movable contactor connected to the tap on said secondary, meansresponsive to the unbalance and phase of current in said connection to position said contactor for balancing the currents in the two parts of the said secondary, and a second resistor shunting said secondary and having a movable contactor adapted for manual setting to establish a standard for the control voltage, said control voltage being available between said second contactor and the mid tap of said secondary, and means actuated by said control voltage to indicate the direction and amount of deviation between said contactors.

4. In apparatus for providing local Or remote control of the standard about which a control potential is automatically adjusted, in combination, a source of control voltage, means for automatically adjusting said voltage in phase and potential, local manual means for determining the standard and including a slide wire and contactor, a remote standard determining means including a slide wire shunting the first slide wire and a second contactor, a switch for selecting the contactor to be used, a magnet for operating said switch, and a control button at each of the local and remote stations-to energize said magnet and a holding circuit for said magnet automatically energized upon movement of the said switch.

5. In apparatus for providing local or remote control of the standard about which a control potential is automatically adjusted, in combination, a source of control voltage, means for automatically adjusting said voltage in phase and potential, local manual means for determining the standard and including a slide wire and contactor, a remote standard determining means including a slide wire shunting the first slide wire and a second contactor, a switch for selecting the contactor to be used, a magnet for operating said switch, a control button at each of the local and remote stations to energize said magnet, a holding circuit for said magnet automatically energized upon movement of the-said switch, a signal means at each station to indicate which contactor is in control, and means actuated by said magnet to control said signal means.

6. In apparatus for providin local or remote control of the standard about which 'a control potential is automatically adjusted, in combination, a source of control voltage, means for automatically adjusting said voltage in phase and potential, local manual means for determining the standard and including a slide wire and contactor, a remote standard determining means including a slide wire shunting the first slide wire and a second contactor, a switch for selecting the contactor to be used, a magnet for" operating said switch, a control button at each of the local and control of the standardabout which a control potential is automatically adjusted, in combination, a source of control voltage, means for automatically adjusting said voltage in phase and potential, local manual means for determining the standard and including a slide wire and contactor, a remote standard determining means including a slide wire shunting the first slide wire and a second contactor, a switch for selecting the contactor to be used, a magnet for operating said switch, a control button at each of the local and remote stations to energize said magnet, a holding circuit for said magnet automatically energized uponimovement of the said switch, a signal means at each station to indicate control by the local station, and a signal means at each station to indicate control by the remote station and a selector switch for energizing the appropriate signals, said signal selector switch being arranged to be actuated by said magnet.

8. In apparatus'for providing local or remote control 01' the standard about which a control potential is automatically adjusted, in combination, a source or control voltage, means for automatically adjusting, said voltage in phase and potential, localrnariual meansfor determining the standard and including a slide wire andcontactor, a remote standard determining means including a slide wire shunting the first slide wire and a second contactona switch for selecting the contactor to be used, a magnet for operating said switch, a control button at each, of the local and remote stations to energize said magnet, a holding circuit for said magnet automatically energized upon movement or the said switch. a signal means at each station toindicate control by the local station, a signal means at each station to indicate contro1 by the remote station, a selector switch for energizing the appropriate signals, said signal selector switch being arranged to be actuated by said magnet, and means to indicate the phase and potential of said control po- 10 ing a pair of A. C. energized triodes and a zerocenter D. C. voltmeter connected between the cathodes thereof.

9.- Apparatus for providing regulation of a control voltage from remote locations comprising, in combination, a first slidewire having an adjustable contact, a second slidewire located adjacent said first slidewire and having an adjustable contact, a third slidewire located at a remote location and having an adjustable contact, means for connecting said slidewires in parallel with each other, means for connecting the ends of said slidewires to a source of A.-C., a switch havin contacts connected to the adjustable contacts of said second and third slidewires, a switch element movable selectively into engagement with the switch contacts, a control voltage output circuit connected to the contact of said first slidewire and to said switch element, and two-way rectifying and amplifying means connected across said .output circuit at said remote location to indicate the phase and potential of the control voltage.

10. The apparatus of claim 9 including a solenoid for controlling said switch element, a control circuit for said solenoid including push buttons at each of said locations, a second switch element actuatedfby said solenoid and controlling a holding circuit therefor, signal means at each of said locations for indicating the location at balance and phase or current in said connection to position said contactor for balancin the currents in the .two parts of the said secondary, a second resistor shunting said secondary and having a movable contactor adapted for manual setting to establish a standard for the control voltage, said control voltage being available between said second contactor and the mid tap or said secondary, and means actuated under the control of said control voltage.

ANTHONY J. HORNFECK.

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